1. Field of the Invention
The present invention relates to a traveling control system for a motor vehicle and, in particular, to a traveling vehicle which can follow another vehicle traveling ahead of the vehicle and avoid contact with the other vehicle.
2. Description of the Related Art
The conventional obstacle detection system used in such a traveling control system for a motor vehicle is disclosed in for example Japanese Patent Publication No. 51-7892. The conventional obstacle detection system includes a radar device which detects an obstacle such as a vehicle traveling ahead by transmitting radar waves such as an ultrasonic wave and an electric wave toward the front direction of the vehicle, a rotation device for rotating the radar device in a horizontal direction, and a steering sensor for detecting a steering angle of the vehicle. According to the steering angle detected by the steering sensor, the radar device is rotated through the predetermined horizontal angle by the rotation device and the radar wave is transmitted in the same direction as the direction in which the vehicle is traveling.
Recently a scanning-type radar device has been developed. The scanning-type radar device scans a wide scope in the horizontal direction and picks up only the information of the obstacle located on an traveling course on which the vehicle is supposed to travel thereafter. The traveling course is estimated by the driving conditions of the vehicle such as a steering angle and/or a vehicle speed.
The above-mentioned conventional obstacle detection system estimates the traveling course, based on the driving conditions of the vehicle, when the radar device detects another vehicle traveling ahead on the estimated traveling course. Therefore, there is a problem in the conventional obstacle detection system. Namely, when another vehicle traveling ahead goes into the curved road from the straight road and the vehicle equipped with the detection system is still traveling on the straight road, the other vehicle traveling ahead has left the estimated traveling course. As a result, the vehicle with the detection system can not detect in an early stage a vehicle which newly enters into the curved road and travels between the other vehicle ahead and the vehicle with the detection system.